Although the chemical identity of thyrotropin releasing factor (TRF) has been known for some time, relatively little is known about the neuron which produces this peptide. The mechanism by which TRF is synthesized is still not known nor do we know how the peptide is stored inside the peptidergic neuron. The regulation of its release from the neuron and the mechanism of release are poorly understood. Furthermore, although it is known that TRF is capable of altering the electrical activity of some central nervous system neurons, the molecular mechanism of this action of TRF is not understood. In this proposed study, the factors controlling TRF release from the peptidergic neuron will be investigated using in vitro model systems of varying complexity (from a TRF-producing clonal cell line to a hypothalamo-median eminence explant from the frog). The effect of putative neurotransmitter agents and thyroid hormones on the TRF release from these model systems will be studied. The ionic requirements for basal and stimulus-induced TRF release will be examined. In order to investigate the mechanism by which TRF alters the function of central nervous system neurons, the action of this peptide alone or in combination with putative neurotransmitter agents on the electrical activity of identifiable neurons from the gastropod Lymnae stagnicola will be studied using intracellular recording techniques. A possible interaction of TRF with the monoamine-sensitive adenyl cyclase system in these neurons will also be studied by measuring the effect of TRF alone or in combination with monamines on the cyclic AMP content of in vitro incubated circumesophageal ganglia from Lymnae stagnalis. 9